1. Field of the Invention
The present invention relates to a magnetic recording medium incorporating a non-magnetic support member on which a thin metal magnetic film is formed, and more particularly to a magnetic recording medium for use as a video tape which is capable of recording data for a long time or a taper streamer having a large capacity.
2. Description of the Related Art
Hitherto, a support member for a thin metal-magnetic-film magnetic recording medium has been mainly composed of polyethylene terephthalate film because of relatively satisfactory strength of its material and dimension stability. In particular, a home video cassette tape, for example, 8 mm-tape has been constituted by a polyethylene terephthalate film having a thickness of about 7 .mu.m to about 10 .mu.m. The tape streamer incorporates the polyethylene terephthalate film of a type having a thickness of about 5 .mu.m to about 7 .mu.m.
In recent years, the cassette size of each of DVC (Digital Video Cassette) tapes among the video cassette tapes has been reduced. A longer recording operation has been required. Also in the industrial field of the tape streamer tape including D8 (Data 8 mm) and DDS (Digital Data Storage), larger capacity has been required.
To realize the long recording operation and enlargement of the capacity of the magnetic recording medium, the thickness of the base film must be reduced. Reduction in the thickness, however, encounters a problem in that the stiffness of the magnetic recording medium is decreased and the skew characteristic deteriorates.
To realize satisfactorily high stiffness and a sense amplifier skew characteristic, contradictory characteristics, that is, the base film must have high strength and resistance against heat shrinkage, must simultaneously be satisfied. Therefore, the polyethylene terephthalate film has been subjected to a re-orienting process or the like to increase the strength. Moreover, an aging process or the like has been performed to prevent heat shrinkage.
Recently the strength of the polyethylene terephthalate film is limited because the thickness of the film has furthermore been reduced. As a next generation of a base film for a high-density magnetic recording medium, an aromatic polyamide film exhibiting high strength and restrained heat shrinkage has attracted attention.
Since long-time recording and enlargement of the capacity have been realized, the magnetic recording medium must have furthermore improved characteristics. That is, the magnetic recording medium must have a furthermore improved electromagnetic conversion characteristic and a reduced error rate.
From the above-mentioned viewpoints, it is preferable that the surface of the base film is a flat mirror surface which is free from any projection. An evaporated film formed on the foregoing base film, however, suffers from unsatisfactory movement characteristic because the mirror surface of the base film is maintained. Thus, there arises a problem in that a scuff occurs and the error rate is undesirably raised owing to separation of powder from the evaporated film.